Conventionally, most chemicals known as pest repellents are volatile or sublime, and when they are applied to processed products such as fiber products, resin molded articles, electronic equipment, and print inks, they instantaneously dissipate due to heat, solvent, etc. during processing, the effect is lost, and the human body and the environment are badly affected.
As measures for such problems, JP-A-3-161402 (JP-A denotes a Japanese unexamined patent application publication) discloses a cockroach repellent in which release of a chemical is suppressed by covering with a metal foil one side of a plate formed by kneading a pyrethroid-based insect repellent into a synthetic resin; however, due to the shape being restricted the application thereof is also limited, and since resistance to heat or solvent during molding or processing is not improved, there is the unsolved problem that even when one side of the plate is covered, the chemical is easily released and lost from the opposite side.
Furthermore, JP-A-2000-302613 discloses a repellent in which a pyrethroid-based compound is supported on a layered phosphate or a layered silicate, thus imparting heat resistance and persistence. Although a pyrethroid-based compound has an insecticidal effect, its repellent effect is weak at room temperature, resistant insects emerge, there is a problem with safety, etc., and the range of applications is limited.
JP-A-09-031245 proposes a slow-acting function-imparting agent in which an organic function-imparting agent is supported on a water-absorbing inorganic substance having the ability to bind water of crystallization, and there is an example in which persistence with an effect after 500 hours in a weather resistance test is exhibited by subjecting a synthetic hydrotalcite or a Y-type zeolite to an exhaustive treatment with N,N-diethyl-m-toluamide and carrying out kneading into a polypropylene resin at 250° C. However, since N,N-diethyl-m-toluamide cannot easily be immobilized between layers of a synthetic hydrotalcite or within pores of a Y-type zeolite, this exhaustive treatment does not give sufficient durability to a chemical, and it is an imperfect treatment that gives no more than a simple mixture of a chemical and an inorganic support.
A complex formed by utilizing simple physical adsorption onto a substrate surface might exhibit some degree of gradual release due to the adsorptive power, but since physical adsorption is not accompanied by a large energy such as a change in the crystal structure or chemical bonding, it cannot exhibit a large change in heat resistant temperature or marked durability. In reality, it cannot be said that this exhaustive treatment gives sufficient durability, and there are problems such as foaming being caused if the molding temperature or molding retention time is increased, and bleed-out being caused if a molded article is stored indoors for a long period.
Furthermore, Pharmaceutical and Food Safety Bureau Notification No. 0824003 issued by the Ministry of Health, Labour, and Welfare on 24 Aug. 2005 states that attention should be given to the safety of N,N-diethyl-m-toluamide, and there is a need for a pest repellent having not only high durability but also high safety.
As an example involving something other than simple physical adsorption onto a solid surface, JP-A-2007-291097 proposes a clay mineral-based complex material in which a clay mineral having cation exchangeability between layers is used as a main starting material, and with regard to a combination of an alkali or alkaline earth metal and a bioactive organic compound, which replaces interlayer water between the layers, the organic compound is incorporated between the layers in a stable or semi-stable state. Specifically, a clay mineral-based complex material is cited as an example that can maintain insect repellency for a long period by incorporating N,N-diethyl-m-toluamide, which is a pest repellent, between layers of montmorillonite, which is a clay mineral.
In this treatment, a powder X-ray diffraction analysis of the complex confirmed that the organic chemical is present between the layers of the clay mineral, and although the stability at room temperature is excellent, it cannot be said that it has excellent heat resistance and sufficient durability. Furthermore, since a natural clay mineral is used as a starting material, there is the problem of a resin being colored. That is, although including an organic chemical between layers of an inorganic compound having a layered structure was attempted, due to the selection of the inorganic compound and the organic chemical being poor, the durability of the complex was insufficient, and there was a problem with coloration.